Expansible last or boot-tree



pt. 26, 1933. F. MERZ M 85 EXPANSIBLE LAST OR BOOT TREE Filed Nov. 20, 1929 2 Sheets-Sheet 1 Sept. 26, 1933. F. MERZ EXPANSIBLE LAST OR BOOT TREE Filed Nov. 20, 1929 2 Sheets-Sheet 2 Inventor Patented Sept. 26,1933 1 EXPANSIBLE LAST 0R, BOOT-TREE Fritz Merz, Frankfort-on-the Main-Rodelheim Germany I Application November 20, 1929, Serial No.

408,604, and in Germany November 24, 1928.

. l Glaim.

The present invention relates to an expansible last or boot-tree on which a spring is arranged between the heel section and toe-section, which spring in operative position has a curved shape.

To known lasts of the above named kind the drawback is, thatthey not only exert a pressure upon the toe and heel parts of the shoe but also tend to press the upper leather upward, whereby the front part of the shoe is forced upward and stretched and widened in an undesired manner.

This eifect of the known shoe expanders or boot-trees is due to the manner in which the stretching spring is connected to the last body. The spring was hitherto arranged in such relation to the last body, that the spring in non-operative position, i. e. in stretched state was lying parallel or substantially parallel to the bottom plane of the last body. Fig. 1 shows a last of the above mentioned kind, consisting of a last body a and a spring I). When this device is placed in a shoe the spring will be deformed as indicated in Fig. 2 andpartially show a negative, partially a positive curvature. I

In order that the'invention-may be thoroughly understood it is thought advantageous to examine the conditions of balance of a springarrangement of the above named kind. If the greater part of. the upper leatherof the shoe were removed and only a small cap left, for contact with the tip of the last body, the entire systern would behave as if thetip and theheel section were rotatably arrangedin a kind of a ball and socket joints, whereby however the span between the heel and the tip would remain constant. In such an arrangement the lastbody will, with respect. to the transmission of force and the dynamic behaviour, act as a rigid rod.

The dynamic behaviour of the shoe expander is shown graphically in Fig. 3, in which (1. denotes the last body, B the tip of the same, bthe spring and C the heel section. The' distance B'-C will always remain constant for one and the same shoe. It should be noted, that the spring b is rigidly connected to the body a, so that the end portion of the spring I) in the point A, always will form the same angle with the line A B. As shown in the Figs. 2 and 3 the springb shows adouble continuous curvature in negative andpositive sense, and is therefore not in a state of balance. The spring I) and the portionpa in the position C A B will always tend to deflect and if this deflection is not prevented the point A will move along a circular arc with the centre B until the spring only is curved in a single sense. This position, in, which the device (1,1) only exerts a stretching effect without tending to deflect is denoted A If one would try to move this point from the position A into the position A by hand, the Vertex point or" the spring would be shifted towards the connection point between the spring and the last body. In this position the energy stored in the spring willbe greater than in the position A wherefore the system, if left to itself, will return to position A. If the spring were linkedly connected to the body a in the. point A it would of course behave in an entirely different manner, in that the junction point A would move,

along a circular are about the centre B until the spring would be fully stretched.

The shoe expander shown in Fig. 1 would, if inserted into a shoe, try to take up a position similar to the position B-A-C of the device a, b

in Fig. 3 and thereby exert a pressure on the toe part of the shoe, whereby this is widened.

It follows from the above consideration, that a state of balance may be obtained even if the end of the spring is rigidly connected to the last body. If this state of balance shall be obtained in a position of the device in which the last body rests securely without pressure on the sole of the shoe, thespring must however be fastened to the last body at such an angle, that the spring in operative position is curved in a single sense and for instance curved in the manner of [the spring C-A in Fig. 3. If the angle at which the spring is attached to the last body is smaller than the angle representing the state ofbalance. the spring will take up the form shown in Fig. 2, whereby a component of pressure in the direction of the upper leather will be created. If the said angle is made greater than the angle representing the state of balance, the spring will take up the form of the curve (I A in Fig. 3 and will tend to deflect the last body towards the sole of the shoe. i

Fig. 3 shows, that a shoe expander or last at a fixed span B-C, a fixed length of the last body a and the spring b and a fixed angle of connection between the spring and the last body can only be brought into a state of balance at a certain value of the difierence of height between the points 3 and C, i. e. between the toe and heel parts of the shoe. Now, lasts of this kind are usually not manufactured separately for each type ,of shoes onthe market and the same lastpmust therefore be employable for shoes of different heights of heels and different spans. The lasts are therefore suitably adjusted in such a manner, that the above named angle of connection is somewhat greater than that representing the stateoi haliii) ance for a normal shoe. In this case the spring will in operative position be formed like the curve C--A in Fig. 3, and the last body will exert a light pressure against the sole, which will be of little or no consequence. Even if a last of this kind is used in a shoe having a shorter span or a higher heel, no pressure will be exerted on the upper leather, because the device is so dimensioned that the state of balance for a normal shoe is surpassed. When used in a shoe the heel of which is higher than that of the normal shoe for which the device is designed, the latter will therefore be brought nearer the state of balance, without surpassing the same.

According to the present invention the spring is connected to the last body at such an angle that the spring of the device, when the latter is placed in a shoe, holds the last body in a position of balance or in a position in which the state of balance is surpassed, so that the last body presses against the sole of the shoe.

Some constructional forms of the invention are shown by way of examples in the accompanying drawings.

Figs. 1-3 illustrate diagrammatically the novel technical effect brought forth by the invention.

Fig. 4 is a side view, partially in section, of a last according to the invention in operative posi tion in a shoe.

Fig. 5 shows a detail.

Fig. 6 is a side view of another constructional form of the invention having a rotatable link connection or coupling between the last body and the spring, which coupling may be fixed in any desired position.

Fig. 7 is a perspective view of the said coupling member.

Fig. 8 shows on a reduced scale the last according to Fig. 6 in collapsed state.

Fig. 9 is a side view of a further constructional form of the invention having a knee joint between the spring and the last body.

Fig. 10 is a lateral view of a constructional form of the invention having an adjustable cou pling between the spring and the last body.

Fig. 11 is a front view of the same device.

Fig. 120; shows the device of Figs. 10 and 11 with opened joint.

Fig. l2b shows a further adjustment of the device illustrated in the Figs. 1012.

In Fig. 4 a denotes the last body, I) the spring and c'the heel member. The spring is connected to the last body in such a manner, that it in its position of rest is nearly perpendicular to the bottom face of the last body.

When this last is inserted into the shoe the spring will form only a single curve when the last body takes up such a position that it rests securely on-the sole of the shoe. The last body is therefore not subjected to any lifting action and the upper leather is not widened or stretched. The device shown in Fig. 4 is for the shoe indicated in connection therewith adjusted for a position somewhat above the position of balance and may therefore also be used with advantage for shoes having heels of different height and having an other span without the upper leather being unvice will only take up a very little space when being packed.

The expansible last shown in Fig. 4 is suitably arranged in such a manner, that the angle of connection between the spring and the last body is somewhat smaller than the angle which represents the position of balance for a normal shoe. The device may therefore also be used for shoes the form of which deviate somewhat from the normal form. A last of this kind tends to exert a pressure on the sole of the shoe. With light shoes it is however desirable to employ a last, which is adjusted exactly to the position of balance, so that it only will exert a stretching effect between the heel and the tip of the shoe. It is possible to arrange lasts of the above named kind in such a manner, that only a stretching effect is obtained, but it will in this case be necessary to produce a great number of differently arranged lasts, because each height of heel and each length of span will require a last of special construction.

According to the present invention the number of different lasts which must be held in stock is reduced by connecting the spring with the last body by means of a pivoted connection, which may be locked in any desired position. An expansible last of this kind is shown in Fig. 6 in which a is the last body, I) the spring, 0 the heel member and d the adjustable and lockable connecting piece. to adjust the last at the point of balance for a great number of differently formed shoes, in which it will ther fore only exert a stretching effect on the tip and the heel of the shoe without-damaging the sole or the upper leather. The last may for instance be set or adjusted in the following manner: The shoe is placed on a table or an other support and the last body is inserted into the shoe and-brought into operative position in the same. The last body is thereupon held in. this position and the connecting link (1 is loosened, whereupon the heel member is brought into position. The spring will now automatically adjust itself in the position of balance. When the connecting piece is fixed and after this the body a is left-to itself the device will in no way influence the sole or the upper leather.

As long as the device is used with the same shoe a readjustment of the same, i. e. a loosening of the connection will not be necessary.

The last according to the present invention may of course be adjusted, and fixed in any ed operative position. If it for instance is to or widen the upper leather the angle between the last body and the spring is made larger than the corresponding angle at the position of balance. If on the contrary the said angle is smaller the last body will exert a pressure on the sole of the shoe. An adjustment at which this effect is created is indicated in dash lines. in Fig. 6.

Compared with the constructional forms illustrated in Figs. 4 and 5, the forms of the invention which are equipped with a lockable connecting link possesses the further advantage that they may be packed and delivered in collapsed state, as indicated inFig. 8.

The form and arrangement of the pivotal connecting links may be varied in many ways. The constructional form shown as an example in Fig. 7 comprises two cooperating toothed discs al d which are equipped with arms and are arranged on a threaded pivot or pin 6. The discs may be locked to each other by means of the nut 6 The adjustments are effected by loosen- The element d makes it possible i ing the nut e and separating and turning the discs d? and d relatively to each other until the desired angular adjustment has been .obtained, whereupon the toothed partsof both discs again are brought into engagement with each other and the nut e is drawn tight; The Figs. 6 and '7 show clearly in which manner the connecting link it is fastened'to the last body aand to the spring b. The links d may for instance be pressed or stamped from sheet metal. v

According to Fig. 9 a toggle joint is arranged between the lastbody a and the spring I). The

element e of the joint which is connected to the last body is formed with a U-shaped part which serves as a bearing for a pin on which the element e connected to the spring I: may be rotated and which further guides the element c during its movements. The rotation of the element 2 is limited by a stop e on the same, which at a certain position of the said element e will abut against the U-shaped part of the element e The stop 2 is arranged in such a position, that the last when inserted in theshoe, will be in the position of balance or will press lightly against the sole of the shoe.

The Figs. 10-121) show a joint arrangement by means of which diiferent adjustments may can be locked in such position, that the spring be performed. At one adjustmentvthe angular position of the spring relatively to the last body is such, that the device, when inserted into a shoe, will take up the position of balance or will press lightly against the sole ofthe shoe. At an other adjustment of this device the link The bearing fork f is preferably U-shaped and is connected to the body aby means of a part F. The disc g is for instance connected to the spring b by means of a threaded pin and'is rotatably connected to the fork f by means of a pin h 10- cated in the same. 1 t

The lower part of the fork f carries a locking pin 2', which by means of a threaded part i is guidedin one of the legs of the fork f (Fig. 11). As will be seen from Fig. 11 the threaded part i of the said pin is of the. smaller diameter than the non-threaded part i of the same, which is passed through the other leg or tine of the fork and which at its end is equipped with a button. The length of the threaded part i of the pin is so dimensioned, that the other part 2' of the same may be completely removed from the bearing slot in the fork f. The free end of the threaded part i is preferably'thickened in order to prevent the pin from dropping out of its support.

The cam disc 9 is formed with a cam 9 and a groove g If the locking pin is positioned as shown in Fig. 11 and the spring I) is swung out of the stop 9 of the cam disc Q will abut against the part i of the pin 2, whereby a further opening of the link mechanism is prevented (Fig. 12a). The stop 9' is so arranged, that the device at the angular position of the spring shown in Fig. 12a will take up a balanced position or exert a light pressure on the sole of the shoe.

If the part 2' of the pin is removed from the bearing slot in the fork f the link mechanism may be opened still more. In the position shown in Fig. 12b the part i of the pin 2 may be moved into the groove g whereby the link is fixed in the shown position. In this position of the elements of the device the last body will exert a pressureon the upper leather of the shoe. This position may in many cases be of use, for instance, with new shoes. As soon as the upper leather has been sufiiciently widened the device may for instance by readjustment be brought into the position shown in Fig. 12a.

The last bodies a and the heel members 0 may in all constructional forms of the invention be produced from wood, metal, fiber, vulcanized in after fiexure, adjustable clamp devices fixed onthe last body and the front end of the spring,

and means for holding said clamp devices fixedly in adjusted position to hold the body and said.

front end at such a relative angle that the rear end of the last body can exert no upwardly directed pressure againstthe upper of the shoe and to prevent relative angular movement between said body and said front end whereby such up- 

